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what is the difference between 420a head and 4g63 head

mjboehm

Proven Member
229
3
Oct 18, 2006
Fort Myers, Florida
I was wonder what the difference is between the 4g63 turbo head and a 420a n/t head.
Any info would be great.Thanks
 

gst25401

Proven Member
80
1
Oct 31, 2005
martinsburg, West_Virginia
I really don' t think you can compare the two. They are no way near the same.
 

tqmx1

Proven Member
668
3
Jan 17, 2007
Sacramento, California
Simeralties, Well they are both made out of Aluminum and that is about it. Diffreances apples & oranges. Like trying to put a Ford head on a Chevy IT AIN'T GOING TO FIT!!
 

mjboehm

Proven Member
229
3
Oct 18, 2006
Fort Myers, Florida
The reason I was asking is that I have a head that fits on my 4g63 block, but my cams fit but when you tighten down the camS they won't spin.Any suggestion would be great.
 

tqmx1

Proven Member
668
3
Jan 17, 2007
Sacramento, California
The reason I was asking is that I have a head that fits on my 4g63 block, but my cams fit but when you tighten down the camS they won't spin.Any suggestion would be great.

1 Did the head & cam caps come as a mached set? If yes press on, no ,scrap the head and start over the head and caps are a matched set from the factory. If yes did you get the caps back on in the proper order intake to the back of the engine and #from left to right.

2 Is the head togther? Ie all the valves rockers ect. you might try removing the rockers lube up the cam and try it agan (there is a lot of restance with all the valve train in place) if it turns free it's just valve train restance.

I hope that helps
 

mjboehm

Proven Member
229
3
Oct 18, 2006
Fort Myers, Florida
Yes, the caps are the ones that came with the head, the head is together far as valves,springs in stuff like that but no rocker,lifters and etc. The caps are in the correct order. Like I stated before when you tighten down the caps the cams won't spin. The head bolts up to the block and everthing. It look like my other turbo head but the cams won't fit any suggestion on what car it could it be from?
 

tqmx1

Proven Member
668
3
Jan 17, 2007
Sacramento, California
Man something must be katteywampus. Remove the cam or cams (witch ever one is binding) and run a straightedge across the journals and see if there are any high spots that could be putting the cams in a bind (18" metal ruler)

The head could have been overheated and warped the bejesus out of it.

Better yet remove the head take it back where you got it ( take the cams with you) and see what they think.

The engine has not been fired so when you put it back together they (the gaskets) can be reused.
 

fourreGsixty3

Proven Member
1,807
31
Feb 4, 2006
Essex, Connecticut
How are you going to run a straight edge over a curved surface? It doesnt work. There is how ever a "straight edge, thats a round long piece of solid piping, and thats whats used for checking journals. Check the journals without the bearings, and with the bearings.

What are you torquing the cam caps down to down to?

It should be 15ft/lbs. if your just going, and tightening the holy hell out of them, then thats your problem; if thats what you did there is a very good possibility that you can junk those bearing's.
 

tqmx1

Proven Member
668
3
Jan 17, 2007
Sacramento, California
Straight edge works like a champ just like doing the head gasket surface. Lay the strate edge vertical in the base of the cam (or any other journals and try to fit a feeler guage under it.

And by the way the cams are running aluminum on steel (not a bearing in sight):thumb:
 

fourreGsixty3

Proven Member
1,807
31
Feb 4, 2006
Essex, Connecticut
HAHA good catch. I was thinking between cranks, and cam's. My mistake. I've found that the round straight edge works a lot better, and is MUCH easier for someone who has never done it before. But still over tightening the cam caps will do that same thing as I stated above BUT witout the bearing bit.ROFL
 

mjboehm

Proven Member
229
3
Oct 18, 2006
Fort Myers, Florida
I put the cams in the head, I finger tighten the cams and they barely spin, I torqued them down to the specs that was in the manual and the won't spin.The head was rebuilt at a machine and they told me that everything was fine so I don't know what I am going to do with this head, The machine shop told me they could line bore the head which would be very expensive. Any other suggestion would be great. Thanks for the help.
 
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